Cnidaria is a phylum within Kingdom Animalia which consists of hydras, jellies (or jellyfish), sea anemones, and corals. All cnidarians are radially symmetrical, and there are two main radially symmetrical body types.
The stock market crash, on black Tuesday (October 29, 1929) began the Great Depression.
In the United States, the Great Depression is associated with Black Tuesday, the stock market crash of October 29, 1929, although the country entered a recession months before the crash. Herbert Hoover was then President of the United States.